1. Field of the Invention
This invention relates to a thermal interface material (TIM). More particularly, this invention relates to a TIM comprising a cured silicone prepared by curing a curable silicone composition (“composition”) comprising an organic plasticizer, a thermally conductive filler, and a curable silicone composition.
2. Background
(Opto)electronic components such as semiconductors, transistors, integrated circuits (ICs), discrete devices, light emitting diodes (LEDs), and others known in the art are designed to operate at a normal operating temperature or within a normal operating temperature range. However, the operation of an (opto)electronic component generates heat. If sufficient heat is not removed, the (opto)electronic component will operate at a temperature significantly above its normal operating temperature. Excessive temperatures can adversely affect performance of the (opto)electronic component and operation of the device associated therewith and negatively impact mean time between failures.
To avoid these problems, heat can be removed by thermal conduction from the (opto)electronic component to a heat sink. The heat sink can then be cooled by any convenient means such as convection or radiation techniques. During thermal conduction, heat can be transferred from the (opto)electronic component to the heat sink by surface contact between the (opto)electronic component and the heat sink or by contact of the (opto)electronic component and heat sink with a TIM (TIM1 application). Alternatively, the TIM may be in contact with the heat sink and another component in the (opto)electronic device, e.g., a heat spreader such as a lid or cover (TIM2 application).
Surfaces of the (opto)electronic component and the heat sink are typically not completely smooth, therefore, it is difficult to achieve full contact between the surfaces. Air spaces, which are poor thermal conductors, appear between the surfaces and impede the removal of heat. Inserting a TIM between the surfaces of the (opto)electronic component and heat sink can fill these spaces to promote efficient heat transfer. The lower the thermal impedance of the TIM, the greater the heat flow from the (opto)electronic component to the heat sink.
Most TIMs are based on thermosetting or thermoplastic polymeric matrices. However, the thermal conductivity of conformable polymers is rather low, typically in the range of 0.15 to 0.30 W/mK. To increase the thermal conductivity of the TIM, thermally conductive fillers can be added to the polymeric matrices. The thermal conductivity of these filled TIMs depends on various factors including the thermal conductivity of filler and the packing of filler in the polymeric matrix as dictated by filler particle size and filler particle size distribution.
The effectiveness of the heat transfer between two substrates through the TIM is expressed in terms of thermal impedance or thermal resistance. The thermal impedance or thermal resistance is the summation of bulk resistance of the TIM and interfacial resistance between the TIM and the substrates. There is a continuing need in the (opto)electronics industry to produce TIMs having higher thermal conductivity, lower thermal impedance, with the ability to stay in place for the useful live of the (opto)electronic device. There is a continuing need in the (opto)electronics industry to produce TIMs with low softness, high compressibility, and low bleed out of impurities to increase thermal conductivity and lower thermal impedance.